Department of Biological Science, Florida State University.
Department of Scientific Computing, Florida State University.
Mol Biol Evol. 2015 Apr;32(4):859-70. doi: 10.1093/molbev/msv010. Epub 2015 Jan 23.
Sperm and eggs have interacting proteins on their surfaces that influence their compatibility during fertilization. These proteins are often polymorphic within species, producing variation in gamete affinities. We first demonstrate the fitness consequences of various sperm bindin protein (Bindin) variants in the sea urchin Strongylocentrotus purpuratus, and assortative mating between males and females based on their sperm Bindin genotype. This empirical finding of assortative mating based on sperm Bindin genotype could arise by linkage disequilibrium (LD) between interacting sperm and egg recognition loci. We then examine sequence variation in eight exons of the sea urchin egg receptor for sperm Bindin (EBR1). We find little evidence of LD among the eight exons of EBR1, yet strong evidence for LD between sperm Bindin and EBR1 overall, and varying degrees of LD between sperm Bindin among the eight exons. We reject the alternate hypotheses of LD driven by shared evolutionary histories, population structure, or close physical linkage between these interacting loci on the genome. The most parsimonious explanation for this pattern of LD is that it represents selection driven by assortative mating based on interactions among these sperm and egg loci. These findings indicate the importance of ongoing sexual selection in the maintenance of protein polymorphisms and LD, and more generally highlight how LD can be used as an indication of current mate choice, as opposed to historic selection.
精子和卵子表面都有相互作用的蛋白质，这些蛋白质在受精过程中影响它们的兼容性。这些蛋白质在物种内通常是多态的，产生配子亲和力的变异。我们首先在海胆 Strongylocentrotus purpuratus 中展示了各种精子结合蛋白（Bindin）变体的适应性后果，以及基于精子 Bindin 基因型的雌雄个体的交配选择性。这种基于精子 Bindin 基因型的交配选择性的经验发现可能是由于相互作用的精子和卵子识别基因座之间的连锁不平衡（LD）引起的。然后，我们检查了海胆精子结合蛋白受体（EBR1）的 8 个外显子的序列变异。我们在外显子 8 中几乎没有发现 LD 的证据，但是在精子 Bindin 和 EBR1 之间存在强烈的 LD 证据，并且在精子 Bindin 之间存在不同程度的 LD。我们拒绝了 LD 由共同进化史、种群结构或这些相互作用的基因座在基因组上的紧密物理连锁驱动的替代假设。这种 LD 模式的最简约解释是，它代表了由这些精子和卵子基因座之间的相互作用驱动的选择性交配选择。这些发现表明，性选择在维持蛋白质多态性和 LD 方面的重要性，更普遍地强调了 LD 如何作为当前配偶选择的指示，而不是历史选择的指示。
